Method of rolling a tubing with a controlled wall thickness



Sept. 22, 1964 w. H. LEINBACH 3,149,512

METHOD OF ROLLING A TUBING WITH A CONTROLLED WALL THICKNESS Filed June 50, 1960 2 Sheets-Sheet 1 IN V EN TOR. Willi am H. L el'nbach W, a 5M A T-TY S.

Sept. 22, 1964 w, H. LEINBACH METHOD OF ROLLING A TUBING WITH A CONTROLLED WALL THICKNESS Filed June'so, 1960 2 Sheets-Sheet 2 INVENTOR. MY/fam f2. Z e/n acb United States Patent 3,149,512 METHOD OF RSLLING A TUBING WiTH A CONTROLLED WALL THICKNESS William H. Leinhach, Rte. 3, Hilisdaie, Mich. Filed June 30, 196i), Ser. No. 40,1324 Claims. (Ci. 8il-61) This invention relates to improvements in rolling forms in metal tubing such as convolutions, threads, splines and the like, and to improved dies for roll ng the tubing to the required form.

l-leretofore, convolutions, such as threads or fins and the like have been rolled on bars and tubing by the use of a series of flat or cylindrical dies appling pressure initially to the ultimate root of the finished form and forcing the material first downwardly and then by constriction of the metal itself, to iiow upwardly into the cavity of the convolution or thread die. In such thread rolling operations, the material is stretched to form the roots of the threads or convolutions first and is then forced or stretched radially outwardly to form the crests of the threads or convolutions, with the result that the threaded or convoluted portion of the material is larger in diameter than the external diameter of the work blank.

In such rolling operations, the part being rolled and formed can be made to pass longitudinally through or between the dies in a continuous operation commonly called thru feed rolling, or can be made to remain free from axial movement between the dies during the rolling process. This last mentioned rolling operation is commonly called a plunge rolling operation.

In rolling tubes by the foregoing processes, the tube has been rolled over a mandrel of the general form of the finished product and the metal is stretched into the cavity of the mandrel to first form the roots of the threads and the stretched material is then forced generally radially outwardly to form the crests of the threads. Such methods have never been satisfactory for rolling forms on tubing, and particularly thin walled tubing because the metal is unduly stretched by the forming operation and the amount of forming possible on a tube is limited by the ability of the metal to resist the action of stretching. The rolls further frequently break through the tubing at the points of pressure, due to the lack of a restricting or supporting force on the tubing on th opposite side thereof from the pressure points.

The principal objects of the invention, therefore, are to remedy the foregoing disadvantages in rolling forms in tubing and to provide a new and improved method of rolling forms in tubing in which the breaking through of the crests of the rolls and the roots of the threads or convolutions formed is eliminated.

A further object of the invention is to provide an improved method of rolling tubing in which the tubing is supported at all points during the application of forming pressure thereto and the direction of the flow of material during the rolling process is controlled to thereby prevent fractures from occurring in the tubing.

A still further object of the invention is to provide a method of rolling tubing and forming threads, convolutions, splines and the like thereon, in which the crests of the convolut-ions, splines or threads are formed to size while supported, and the flanks of the convolutions are then formed while supported, to flow the metal of the tubing along the shanks to the roots thereof, all While opposing the working forces by reacting forces actingin opposite directions to the working forces.

A still further object of the invention is to improve upon the prior methods of rolling forms on tubing by working the tubing along the crests of the forms inwardly along the flanks thereof and attaining a formed tube having a uniform wall with a uniform wall thickness.

3,14%,5i2 Patented Sept. 22, 1964 ice A still further object of the invention is to provide an improved method for rolling helical convolutions, such as threads and the like in tubing, in which the tubing is rolled on a convoluted support of the general form of the convolutions of the finished tubing, and in which rolling pressures are applied on the tubing to first form the crests to size along the crests of the convolutions of the support, and then roll the flanks of the convolutions inwardly along the flanks of the convolutions of the support, all while opposing the rolling working forces by the convoluted surfaces of the support.

A still further object of the invention is to improve upon the methods of rolling tubing heretofore known by supporting a tubular flank on a mandrel having a crest and flanks leading inwardly of said crest, to a root and providing a cavity, flowing the metal first along the crests of the mandrel, and flowing the metal ahead contact points into the cavity of the mandrel, then progressively working the metal inwardly along the flanks of the mandrel and finally working the metal along the roots of the mandrel, all While containing the metal from outward movement with respect to the cavity of the mandrel.

These and other objects of the invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings where- FIGURE 1 is a diagrammatic view generally illustrating a set of roller dies rolling a form on a tubular blank supported on a mandrel;

FIGURE 2 is a diagrammatic view showing a tubular blank supported on a mandrel constructed in accordance with the invention;

FIGURE 3 is a fragmentary diagrammatic sectional view illustrating the form of the roller die and mandrel and showing the roller die in the operation of roll ng threads on a tubular blank supported on the mandrel;

FIGURE 4 is a diagrammatic view illustrating a modified form in which the invention may be embodied; and

FIGURE 5 is a diagrammatic sectional View illustrating the operation of rolling threads on a tubular blank in the form of the invention shown in FIGURE 4.

In the embodiment of the invention illustrated in FIG URES 1, 2 and 3 of the drawings, I have shown in FIG URE- l a tubular blank 1h supported on a mandrel 11 and have shown three roller dies 12 for rolling a form, such as a thread on the tubular blank 10.

The tubular blank 19 may be made from any suitable metal, such as steel, aluminum, brass, copper or any other metal which may be rolled. The external or outer diameter of the tubular blank is greater than the outer diameter of the finished form and the blank should have a wall thickness containing suifi'cient volume, that Will leave a finished wall of a desired thickness, without loss or waste of material, when the blank is worked. The rolls 12' are generally cylindrical in form and may be mounted on and driven from a cylindrical die machine, an automatic screw machine, a turret lathe or like machine in a manner well known to those skilled in the art, so not herein shown or described;

It should be understood, however, that while I have shown three cylindrical dies that I may also use one or two cylindrical. dies and that the dies need not be cylindrical and may be fiat or planetary thread rolling dies, if desired. 7

Where the dies are flat thread rolling dies, a movable die moves past a stationary die. The tubular blank to be rolled is mounted on a mandrel placed between the fiat reciprocating dies and is rolled between the dies to roll a form or forms thereon in the same manner forms are rolled on the tubular blank by the cylindrical dies shown herein. Planetary thread rolling dies also operate on principles similar to fiat thread rolling dies and the threads or convoluted surfaces of the dies are formed in the same manner as the threads or convoluted surfaces of cylindrical dies.

Planetary and flat thread rolling dies are illustrated on pages 52 and 53 of Engineering Data on Thread and Formed Rolling, published by Reed Rolled Thread Die Company of Worcester, Mass, and since the die form and forming or thread rolling principle is the same for fiat and planetary dies as with cylindrical dies, the flat and planetary dies need not herein be shown or described further.

The mandrel 11, as shown in FIGURE 2, has a forward or advance end portion 13 which is threaded or helically convoluted to conform to the finished threads or convolutions to be formed on the tube. The threads or convolutions of the advance end portion 13 of the mandrel are meshed with threads 18 of the cylindrical dies 12, and feed the tubular blank and mandrel to enter the dies 12 during rotation of the dies, it being understood that working on the blank by the rotating dies effects rotation of the blank and mandrel. The threaded end portion 13 terminates at its inner end in a shoulder 15 adapted to be abutted by the end of the tubular blank when mounted on the mandrel 11. The portion of the mandrel 11 rearwardly of the shoulder is formed to conform to the inside diameter of the finished threads or convolutions to be rolled on the tubular blank 10, as diagrammatically shown in FIGURE 3, showing the mandrel 11 with acme threads 21 extending therealong. The form of the threads or convolutions extending along the mandrel, however, may be varied and may be in the form of helical fins or may be of any other desired forms where it is desired to roll various other forms on the tubular blank 10. Each die 12 is in the form of a roll having a tapered or frusto-conical entrant face 19 extending from a leading wall 14 of the die. The frusto-conical entrant face 19 terminates at its large diameter end into a smooth cylindrical die face 16, of a diameter corresponding to the outer diameter of the crest of the thread to be formed on the tube when the die is in its rolling working position. A thread 17 progressively rises out of the cylindrical die face 16 and extends along the die in a helical path to the trailing end of the die. The thread 17, as it rises out of the die face 16, initially has flanks 17a extending parallel to flanks 21a of the thread of the mandrel. The flanks 17a are relatively short compared to the depth of the thread 21 and are connected by a concave face or crest 24. The concave crest 24 extends along the thread until the thread approaches the maximum desired height, as indicated by reference character 18. The concave portion 24 provides relief for the thread of the die and directs the initial points of pressure to the flanks 17a of the thread of the die, rather than on the ultimate root of the tooth of the thread, and enables the flanks to be formed in the blank against the flanks of the mandrel and to be reduced to a uniform thickness prior to forming the root of the blank by the crest of the completed thread 18 of the die. In carrying out the invention, a tubular blank having an outside blank diameter larger than the measured diameter of the form to be imparted on the tubing is placed on the mandrel 11 with an outer end thereof in abutting engagement with the shoulder 15. The mandrel and tube being suitably supported, the threaded portion 13 of the mandrel is threaded between the dies 12, the threads 18 of which are of the pitch diameter of the threads to be formed on the tubular blank 10. The cylindrical dies are then rotatably driven and the mandrel and blank 10 are fed axially between said rolls by the lead of the threads of the threaded end portion 13 meshing with the threads of the rotating dies. The frustoconical entrant face 19 will then initially come into rolling engagement with the leading end of the tube in engagement with the shoulder 15 and will thin the wall of the 4 blank along the crest of the mandrel 11 until the thickness of the wall of the blank has been reduced to the required thickness of the wall of the crest of the completed piece. The metal is thus thinned along the crest of the thread of the mandrel to the required wall thickness of the crest of the thread while supported on the crest of the mandrel and during this thinning operation any surplus metal is progressively flowed ahead of the contact points of the metal with the crest 20 of the thread 21 of the mandrel, into the unfilled spaces between the convolutions of the thread on the mandrel as indicated by reference numerals 25, 26 and 27 in FIGURE 3.

As the blank is being thinned to the thickness of the crest of the finished thread, the surplus metal is flowed into the cavity between the convolutions of the thread of the mandrel ahead of the contact points on the crest and downwardly along the flanks of the thread, to a point where the downward flow of metal along the flanks is restricted by the root of the thread on the mandrel.

The entrant face 19 of the cylindrical die 12 thus applies initial pressure to first form the crest of the thread of the tubular blank against the crest of the mandrel to the desired thickness, while the die surface 16 between convolutions of the thread 17 of the die, contains any upward action of the metal at the time of compressing the metal against the crest of the mandrel. The cylindrical die surface 16 of the die between the teeth 17, thus forces the metal reduced from the crest to flow inwardly into the cavity of the mandrel between the convolutions of thread 21 thereof. As the rolling operation is continued, the die 12 continues to contain the metal from any upward action, while the mandrel 11 supports the metal of all points during working thereof, as the flanks of the teeth on the blank are worked against the flanks of the teeth of the mandrel. During this working operation, the concave portions 24 and the crests of the threads 17 of the cylindrical die assure that the initial points of forming pressure are directed by the flanks 17a against the flanks of the thread of the mandrel, rather than on the ultimate root of the thread, until the thread approaches its finished form.

It should here be noted that as the blank is formed, that the portions of the blank worked are supported on the thread of the mandrel at all working points, and that the mandrel reacts against and directly opposes the pressure being applied by the dies, and that the entire working of the tubular blank is in opposition to the supporting surfaces of the mandrel.

In the modified form of the invention shown in FIG- URES 4 and 5, I have diagrammatically illustrated the process of my invention for rolling threads in tubes from the inside thereof. In this form of the invention, the tubular blank 10 is clamped in a form or mold 30, diagrammatically shown as being in two halves, held together by a nut and eye bolt 31. The mold 36 serves the same purpose as the arbor 11, and has internal threads formed therein corresponding to the external diameter of the threads to be formed in the tube or blank, which support the tubular blank along the crest of the thread,

and accommodate working of the blank inwardly along the thread of the mold to form the flanks and root of the thread in the same manner, as described in the form of my invention diagrammatically illustrated in FIGURE 3.

A rotatably driven die 33 is shown in FIGURE 5 as being rotatable within the blank 10, while the blank is held stationary between the two parts of the mold 30. The die 33 is similar to the cylindrical die 12 and has an inclined entrant face 35 leading to a plane surface 36 having a helical thread 37 leading spirally therefrom and increasing in height to the height of the finished form of the thread to be formed in the blank 10.

The crest of the leading portion of the thread 37 is generally concave in form as indicated by reference chap actor 39, to relieve the crest of the thread in the die and direct the initial points of pressure to the flanks, rather than on the ultimate root of the thread. The crest of the trailing portion of the thread 37 is flat and is of substantially the form of the internal diameter of the finished thread.

In carrying out the thread rolling method of this form of the invention, assuming the blank is clamped to the mold 39, the die 33 is rotatably driven and fed axially of the blank to first the blank by the inclined entrant die face 35, to the internal diameter of the crest of the finished thread and then flow the surplus metal outwardly along the cavity between the flanks of the thread in the mold 30 into the unfilled portions of the mold and work the metal along the flanks of the thread in the mold to the required thickness, determined by the spacing between the thread of the die 33 and the thread in the mold 30, while containing any radiall inward action of the metal by the thread of the die 33, and successively moving the metal to form the root of the thread to the required thickness, all while working under the opposing reactions or pressures of the mold 30.

Where it is desired to roll the tubular blank to a splined or longitudinally ridged form, in cases where it may be desired to use the blank as a hollow splined drive shaft, or as a structural member, the rolling principle is the same as the principle of rolling threads or other helical convolutions in the blank. In rolling splines or ridges in a tube, the mandrel will be splined or ridged, to conform to the internal diameter of the finished splines or ridges. The cylindrical dies, where such dies may be used, however, Will be formed in the same manner as the dies 12, but the lead of the helical thread of the die will be such as to feed the tubular blank 19 axially and roll axially extending splines along the blank from the crests to the roots of the splines, while the blank is supported on the splined mandrel, in the same manner that helical threads or convolutions are rolled on a tubular blank.

It should further be understood that in a tube rolling operation with cylindrical dies, where the threads are rolled along the exterior or" the mandrel that the rolling operation may be a continuous operation and the tubular blank may be fed through the rolls together with its mandrel to the end thereof, the threads being formed in the tube for the full length thereof, where desired. Upon completion of the thread rolling operation, the tubular blank may then be screwed from the mandrel.

It may be seen from the foregoing that a new and improved process has been provided for rolling shapes on tubular blanks which is distinctly diflerent from prior thread rolling processes which displace material from the roots of the threads or convolutions and force the material radially outwardly to form the crests last, in that the process of the invention instead creates and maintains a cavity of the desired form and dimensions and reduces and forms the blank to the desired form and dimensions within this cavity by containing the material as it is flowed to reduce the blank to the proper thickness and form the crests of the thread or convolutions, and by supporting the worked surfaces on the mandrel during the entire forming operation and containing the material from flowing outwardly of the cavity toward the crest of the thread or convolution.

It may further be seen that the process of the invention may readily be adapted for rolling threads, splines, and variou forms on tubing and that the process may be carried out by various types of thread rolling machines by external roller dies, an internal die, or by flat or planetary dies in accordance with the final form to be attained.

It may further be seen that by the process of the invention the material is worked between opposed pressure points, causing the material to flow rather than stretch and preventing the creation of fractures in the wall of the material and increasing the strength of the material.

While I have herein shown and described several forms in which my invention may be embodied, it shold be understood that I do not desire the invention to be limited 5 to the specific forms shown, but that various other variations and modifications in the invention may be attained without departing from the spirit and scope of the novel concepts thereof, as defined by the claims appended hereto.

I claim as my invention:

1. A method of rolling convolutions in cylindrical metal tubing, which consists in providing a rigid convoluted form, the convolutions of which conform generally to the convolutions to be imparted to the finished tubing and which have a crest wit-h flanks leading from said crest to a root, backing a tubular metal blank by said convoluted form and applying rolling forming forces on the blank so backed along the crest of the form to reduce the wall thickness of the blank at the crest to form the crest to the desired wall thickness and during this reducing op eration flowing the metal ahead of the forming forces on the blank and progressively forcing the metal to flow inwardly along the supporting flanks to the root of the convoluted form and then forming the metal along the root of the convolution to the desired wall thickness, all while forcing the metal by the rolling forming forces to flow along the supporting surfaces of the convoluted form during the entire form ng operation.

2. A method of rolling a form in cylindrical metal tubing comprising the steps of mounting a tubular metal blank of a greater outside diameter than the outside diameter to be imparted to the finished tube on a mandrel having a helical crest wit-h flanks leading from said crest to a root, said flank and root defining a helical cavity extending along the mandrel, then working the tubular blank with rolling forming forces only on surfaces supported on the mandrel, and during the working operation first flowing the metal in the blank along the crest of the mandrel to reduce the outside diameter of the blank to the required outside diameter of the finished form and form the crest to the desired wall thickness forcing the metal of the blank into the cavity formed between the two opposing flanks, and progressively flowing the metal reduced from the blank inwardly along the supporting surfaces of the flanks of the mandrel into the cavity thereof, and continuing the progressive flowing of the metal along the flanks of the mandrel to the root thereof and forming the metal along the root of the mandrel, all while supporting the metal on the fianks and crest of the mandrel while working the metal thereon.

3. A method of rolling a cylindrical metal blank into a desired contour, the thickness of the wall of the blank being greater than the wall thickness of the contour to be imparted to the blank, comprising the steps of mounting the blank on a mandrel formed to conform to the inner diameter of the desired con-tour to be imparted to the blank, said mandrel having a crest supporting the blank with fianks leading inwardly of said crest to a root, providing a cylindrical rolling die having a frusto-conical entrant face for initial contact with the blank and merging into a cylindrical surface that progressively changes into the full complement of the desired contour, advancing the mandrel and blank along the rolling die and rolling the advancing blank on the mandrel by the die along the upporting surfaces of the crest of the mandrel to first reduce the blank to the desired thickness of the crests of the contour to be imparted to the blank, and to then flow the metal of the blank along the supporting flanks of the mandrel into the cavity between the flanks and progressively form the metal along the flanks of the mandrel to the root thereof.

4. A method of rolling the wall of a cylindrical tube of ductile material into a convoluted contour, which comprises, mounting the tube on a first rigid forming surface having a crest with flanks leading from the crest to a root, advancing said first rigid surface and tube between a plurality of rotating rigidly backed forming surfaces, said rigidly backed forming surfaces each having a frusto conical entrant surface for initial contact with the ad- 'vancing tube, said frusto-conical entrant surface merging into a smooth cylindrical surface that progressively changes into the full complement of the desired contour of the finished form, said first and second surfaces so interacting as to draw the tube and first surface therebetween to effect the advance thereof and to apply rolling working pressure along successive increments of said tube supported by said first surface, to first progressively re duce the wall thickness of the tube to the required wall thickness along the crest of the rigid forming surface and to flow the ductile material ahead of the forming forces on the tubetand to progressively force the ductile matedie within the 'blank having helical convolutions formed on the surface thereof prog essively increasing in height from the advance to the trailing end of said die to the form of the finished convolution, first compressing the metal of the blank against the crest of the mold and reducing the blank to the desired thickness, while flowing the reduced metal ahead of the working forces and retaining the metal to the mold and progressively forcing the metal of the blank to flow along the flanks of the mold into the root thereof, and finally finishing the root of the convolution along the root of the mold, all while retaining the metal to the mold by the rotating and advancing die.

References Cited in the file of this patent UNITED STATES PATENTS 1,805,126 Barker "n May 12, 1931 2,508,517 Hill May 23, 1950 2,508,518 Hill May 23, 1950 2,586,653 Hill Feb. 19, 1952 2,621,701 Gailbraith Dec. 16, 1952 2,757,706 Johnston Aug. 7, 1956 2,779,223 Schuster Jan. 29, 1957 

1. A METHOD OF ROLLING CONVOLUTIONS IN CYLINDRICAL METAL TUBING, WHICH CONSISTS IN PROVIDING A RIGID CONVOLUTED FORM, THE CONVOLUTIONS OF WHICH CONFORM GENERALLY TO THE CONVOLUTIONS TO BE IMPARTED TO THE FINISHED TUBING AND WHICH HAVE A CREST WITH FLANKS LEADING FORM SAID CREST TO A ROOT, BACKING A TUBULAR METAL BLANK BY SAID CONVOLUTED FORM AND APPLYING ROLLING FORMING FORCES ON THE BLANK SO BACKED ALONG CREST OF THE FORM TO REDUCE THE WALL THICKNESS OF THE BLANK AT THE CREST TO FORM THE CREST TO THE DESIRED WALL THICKNESS AND DURING THIS REDUCING OPERATION FLOWING THE METAL AHEAD OF THE FORMING FORCES ON THE BLANK AND PROGRESSIVELY FORCING THE METAL TO FLOW INWARDLY ALONG THE SUPPORTING FLANKS TO THE ROOT OF THE CONVOLUTED FORM AND THEN FORMING THE METAL ALONG THE ROOT OF THE CONVOLUTION TO THE DESIRED WALL THICKNESS, ALL WHILE FORCING THE METAL BY THE ROLLING FORMING FORCES TO FLOW ALONG THE SUPPORTING SURFACES OF THE CONVOLUTED FORM DURING THE ENTIRE FORMING OPERATION. 